问题 填空题

下列物质中①空气;②可口可乐;③铁粉;④高锰酸钾;⑤四氧化三铁;⑥过氧化氢;⑦水;⑧红磷,其中属于单质的是______,属于混合物的是______,属于纯净物的是______,属于化合物的是______,属于氧化物的是______.

答案

铁粉、红磷都是由同种元素组成的纯净物,属于单质.故填:③⑧.

空气、可口可乐都是由多种物质组成的物质,属于混合物.故填:①②.

铁粉、高锰酸钾、四氧化三铁、过氧化氢、水、红磷都是由一种物质组成的物质,属于纯净物.

故填:③④⑤⑥⑦⑧.

高锰酸钾、四氧化三铁、过氧化氢、水都是由不同种元素组成的纯净物,属于化合物.故填:④⑤⑥⑦

四氧化三铁、过氧化氢、水都是由两种元素组成,其中一种元素是氧元素的化合物,属于氧化物.

故填:⑤⑥⑦.

单项选择题
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The United States counts its population every ten years, and each census reveals that the racial and ethnic mix is changing dramatically, so by the year 2050, the "average" American will not be descended from (1) , but the majority of U. S. residents will trace (2) ancestry to Africa, Asia, the Hispanic world, the Pacific Islands, or the Middle East. Once the United States was a microcosm of European nationalities, (3) the United States is a microcosm of the world. The United States is (4) considered a "melting pot" society by many of its residents. (5) , many people prefer the term "salad bowl." They use this (6) to describe American society. American society will soon be (7) nonwhite. "Melting pot" implies that the different ethnic groups blend together (8) one homogeneous (9) , "salad bowl" (10) that nationalities, like the ingredients in a mixed green salad, retain their cultural (11) . Earlier generations of (12) believed they had to learn English quickly not only to survive but also for (13) .
Now, many immigrant groups do not (14) the same need. Because there are many places in America (15) you can work, shop, get medical care, marry, divorce and die without knowing English. (16) , Chinatown in San Francisco and New York. Also, Los Angeles has many Vietnamese immigrants and immigrants from Mexico. (17) , many immigrant groups want their children to know their (18) culture. Many Hispanics, for instance, want their children to learn (19) English and Spanish and study the Spanish language in school. They are fighting for the (20) to bilingual education in many communities. In many communities they are in the majority.